The present invention generally relates to a wiper, such as the type used to disinfect hard surfaces in food service and medical applications. More particularly, the present invention is directed to a wiper having an anti-microbial agent that can be controllably released over an extended period of time and which remains effective after repeated washings and rinsings.
Microbial contamination can have a detrimental effect on any item ordinarily used by consumers or merchants, particularly items used in the medical and food service industries. For example, due to various bacterial outbreaks, there have been at least 200 food poisoning deaths reported in the last 10 years. Moreover, more Americans die from hospital infections each year than from car accidents and homicides combined.
Much of this contamination occurs due to migration of microorganisms from hard surfaces such as table tops or counter tops to food or to the hands of food handlers and, thence, to the food itself. For example, in the food service industry, contamination commonly occurs on stainless steel surfaces used for food preparation. Various food products are prepared on hard surfaces such as counters, tables, and the like. Bacteria from these products will often collect on such surfaces and, if the surface is not disinfected regularly, will transfer from product to product or from a product to the food handler. Numerous studies indicate that cross-contamination occurs as a result of a microorganism coming into contact with a person""s hands or a cleaning cloth and thereafter contaminating other items touched by the cloth or hands, such as equipment or other surfaces.
As a result, wipers that contain anti-microbial agents have been employed to prevent such surface and cloth contamination. Currently, most of these anti-microbial wipers are impregnated with anti-microbial agents and are delivered to the user in a premoistened form. With these pre-moistened wipers, however, the disinfecting agent within the wiper is commonly readily exhausted after washing and rinsing of the wiper to remove dirt after a period of use. Thus, it is believed that such premoistened wipers either inhibit growth on the wipers and/or the hard surfaces cleaned only mildly or may only be used for a limited number of wipes.
Some anti-microbial wipers have been developed that are not pre-moistened. For example, one such anti-microbial wiper that can be delivered in a dry condition is disclosed in U.S. Pat. No. 5,213,884 to Fellows. In the Fellows patent, a wiper is described that contains a hot melt adhesive powder mixed with a chlorine release agent. The adhesive powder and chlorine release agents are incorporated into a tissue suitable for use in the disinfection of hard surfaces.
Although the wiper disclosed by Fellows can be delivered in a dry form, it apparently fails to provide sufficient disinfection over an extended period of timexe2x80x94similar to pre-moistened wipers. After being contacted with water, the release of the anti-microbial agent in such wipers capable of being delivered in a dry state occurs readily without control. This prevents the wiper from sustaining its anti-microbial activity after repeated washings and rinsings.
Another anti-microbial wiper has been marketed by Pal International Inc. of England under the name WIPEX. According to sales literature, this wiper contains poly(hexamethylenebiguanide hydrochloride), alkyldimethybenzyl ammonium chloride, and the disodium salt of ethylenediaminetetraacetic acid (E.D.T.A.). In addition, the wipes include indicator stripes that are stated to fade gradually as the disinfectants in the wiper are depleted. It is believed that U.S. Pat. No. 4,311,479 to Fenn et al. is related to this particular anti-microbial cloth. It is unclear, however, whether these wipes would prove to be very effective in reducing cellular activity. Also, it is believed that they would retain only limited anti-microbial activity after washing and rinsing.
Accordingly, a need currently exists for a more effective wiper that disinfects hard surfaces and inhibits cross-contamination. In particular, a need exists for a wiper that contains an anti-microbial agent that is slowly released when contacted by water, thereby allowing the wiper to provide an anti-microbial solution and to sustain its anti-microbial effectiveness after repeated washing and rinsing operations.
Accordingly, an object of the present invention is to provide a wiper suitable for use in disinfecting hard surfaces.
It is another object of the present invention to provide a wiper containing an anti-microbial agent that can remain effective after repeated washing and rinsing operations.
Still another object of the present invention is to provide a wiper containing an anti-microbial agent that can remain effective after repeated washing and rinsing by controlling the release rate of the anti-microbial agent.
Yet another object of the present invention is to provide a wiper containing a controlled release anti-microbial agent that is incorporated within a fibrous substrate layer.
It is another object of the present invention to provide a wiper containing a controlled release anti-microbial agent incorporated within a hydrophobic substrate layer that adheres to a fibrous substrate material.
These and other objects of the present invention are achieved by providing a wiper suitable for disinfecting hard surfaces and inhibiting or preventing cross-contamination. A wiper of the present invention generally includes a substrate layer, at least one laminate layer, and an anti-microbial agent which is adhered to the substrate layer.
In accordance with the present invention, any material commonly used in the art to manufacture cleaning cloths, such as wipers, can be used as the substrate material. Commonly, but not restricted to such materials are hydrophobic materials. Generally, the substrate material may have a basis weight of more than about 10 grams per square meter (gsm). In one embodiment of the present invention, the wiper contains a meltblown substrate layer formed from poly(ethylene vinyl acetate) co-polymer (EVA).
In addition to a substrate layer, a wiper of the present invention also contains a laminate layer. In general, a laminate layer of the present invention can include any absorbent material (or if an additional laminate layer is employed, a hydrophobic material) that may be bonded to the substrate layer. For example, in one embodiment, two laminate layers formed from a hydroentangled material sold under the name HYDROKNIT(copyright) and having a basis weight of 49 gsm, are bonded to both surfaces of an EVA meltblown substrate layer. HYDROKNIT(copyright) is further disclosed in U.S. Pat. No. 5,284,703 to Everhart et al. which is incorporated herein in its entirety by reference thereto. In addition, the web can be a co-form material such as disclosed in U.S. Pat. No. 4,100,324 to Anderson et al. and U.S. Pat. No. 5,350,624 to Georger et al., which are incorporated herein in their entireties by reference thereto.
As stated, the substrate layer of the present invention can be hydrophobic. Consequently, such layers can have a substantial effect on water penetration because the layer itself has a thickness. As such, the substrate layer can enhance the ability of a wiper made according to the present invention to operate over an extended period of time after repeated washings and rinsings. In particular, when the substrate layer is hydrophobic, it is believed that the layer can inhibit water from readily migrating out of the wiper, thus providing a longer release time for an anti-microbial agent incorporated therein.
According to the present invention, a subject wiper also includes an anti-microbial agent that can be controllably released over an extended period of time after repeated washing and rinsing. xe2x80x9cRepeated washing and rinsingxe2x80x9d, for purposes of the present invention, generally refers to at least 5 cycles of rinsing the wiper between wiping applications. As used herein a xe2x80x9crinse cyclexe2x80x9d includes the steps of contacting the wiper with water and wringing or squeezing the excess water from the wiper. The anti-microbial agent is generally adhered to the fibers forming the substrate layer. In one particular embodiment, the anti-microbial agent is adhered to meltblown poly(ethylene vinyl acetate) (EVA) fibers.
In general, any anti-microbial agent capable of being controllably released can be used in accordance with the present invention. Some examples of anti-microbial agents that are suitable for use in the present invention include various solid particulate anti-microbial agents such as calcium hypochlorite particles, halogen generating formulations, chlorine dioxide generating formulations, particles containing silver ions, and quaternary amines complexed with a carrier.
In one embodiment of the present invention, an anti-microbial agent such as calcium hypochlorite, having different particle sizes is provided. Because smaller particles generally have higher rates of dissolution than larger particles, control of the release rate of the anti-microbial agent can be achieved through use of such particulates having a size differential.
Another embodiment of the present invention includes particulate forms of an anti-microbial agent that are coated with various polymers so that the particles are at least partially encapsulated. In this embodiment, various amounts and types of coatings may be provided to obtain the particular anti-microbial agent release rate desired. For example, a lower release rate is generally provided by a particle having a thicker or more complete coating, and vice-versa. In addition, mechanisms such as polymerization chemistries, porous absorbents, soluble binders, or combinations thereof, may be employed to modulate the controlled release properties of the anti-microbial agent.
The anti-microbial agent of the present invention may be incorporated into a substrate layer before the fibers comprising the substrate layer have become solidified. In one embodiment, calcium hypochlorite particles are added to unsolidified meltblown poly(ethylene vinyl acetate) fibers during formation of the meltblown substrate layer. The particles may be fed into the stream of meltblown fibers while the fibers are still tacky. If desired, the meltblown substrate layer containing calcium hypochlorite particles adhered to the EVA fibers may be formed directly onto a pre-formed absorbent laminate layer so that no additional adhesive is necessary to bond the laminate and substrate layers together, although the use of a separate adhesive for this purpose is within the scope of the present invention. The meltblown fibers are then allowed to solidify into a meltblown web. If desired, an additional laminate layer comprising the same material as the original laminate layer, or a different material, may be bonded to the other surface of the meltblown substrate layer. The additional laminate layer can be bonded to the substrate layer by any means, for example, by chemical or thermal bonding.
The substrate and the laminate layers of the present invention can also contain chemicals in addition to the anti-microbial agent. Moreover, a visual sensor or dye can be incorporated into one or more of the layers to indicate when the anti-microbial agent has been depleted. Some examples of such visual sensors are provided by the indicators described in U.S. Pat. Nos. 3,704,096; 4,205,043; 5,699,326; 5,317,987; 4,248,597 and 4,311,479, which are incorporated in their entireties by reference thereto. In addition, sodium thiosulfate and various blue dye mechanisms such as those employed herein in the WIPEX(copyright) wipes may also be employed.
Other objects, features and aspects of the present invention are discussed in greater detail below.
Reference now will be made in detail to the embodiments of the invention, one or more examples of which are set forth below. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment, can be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention cover such modifications and variations as come within the scope of the appended claims and their equivalents. Other objects, features and aspects of the present invention are disclosed in or are obvious from the following detailed description. It is to be understood by one of ordinary skill in the art that the present discussion is a description of exemplary embodiments only, and is not intended as limiting the broader aspects of the present invention.
In general, the present invention is directed to a wiper containing an anti-microbial agent that can be released to liquid contained within the wiper after a rinse cycle, where the agent is released at a controlled rate over a period of time. It has been discovered that by using an anti-microbial agent in solid or particulate form, the anti-microbial agent is slowly released when contacted by water. Surprisingly, this permits stronger anti-microbial agents to be employed than would be possible with wipers that do not control the release rate of the agent. Moreover, it has been found that the wiper can retain its anti-microbial activity over the course of multiple rinsing cycles. In fact, with certain embodiments of the present invention, as many as 6 or more rinsing cycles are possible. In other embodiments of the present invention, 10 or more rinsing cycles are possible, while in other embodiments of the present invention, 15 to 20 rinsing cycles can be obtained, and even 20 or more rinsing cycles are possible.
In accordance with the present invention, an anti-microbial surface wiper is provided that contains a substrate layer, at least one laminate layer, and an anti-microbial agent. In one embodiment, a wiper of the present invention includes a substrate layer that bonds with a first and second laminate layer. Further, an anti-microbial agent can be incorporated into the substrate layer such that the agent can be released at a controlled rate when contacted with water.
A laminate layer of the present invention can generally be made from any absorbent material commonly used in the art for wipers. For example, a laminate layer of the present invention can be made from absorbent nonwoven fabrics, and more particularly, from absorbent nonwoven composite fabrics having a high pulp concentration. Some examples of laminate layers that are suitable for use in the present invention are disclosed in U.S. Pat. No. 5,389,202 to Everhart et al., U.S. Pat. No. 5,284,703 to Everhart et al., and U.S. Pat. No. 5,573,841 to Adam et al., which are incorporated herein in their entireties by reference thereto. In one embodiment, the laminate layer(s) comprises a HYDROKNIT(copyright) nonwoven composite fabric that contains approximately 70% by weight pulp fibers that are hydraulically entangled into a continuous filament substrate. HYDROKNIT(copyright) material is commercially available from Kimberly-Clark Corporation of Neenah, Wis. In addition, the web can be a co-form material such as disclosed in U.S. Pat. Nos. 4,100,324 to Anderson et al. and U.S. Pat. No. 5,350,624 to Georger et al., which are incorporated herein in their entireties by reference thereto. The wipers may be packaged and made according to the disclosures of U.S. Pat. Nos. 4,833,003 and 4,853,281 to Win et al.
Depending on the particular application, the basis weight of a laminate layer used in accordance with the present invention can vary. In general, the basis weight of the laminate layer incorporated into a wiper of the present invention is at least about 10 grams per square meter (gsm). The basis weight of such laminate layer can also be at least about 20 gsm. In one embodiment of the present invention, the basis weight of the material used for the laminate layer is about 49 gsm.
Although not required, a wiper of the present invention may include more than one laminate layer. In one embodiment of the present invention, for example, the wiper includes two laminate layers, both of which can be made from an absorbent nonwoven fabric, such as a HYDROKNIT(copyright) material. In other embodiments, the additional laminate layer may itself be a hydrophobic material like one embodiment of the substrate layer. This allows the wiper to be engineered for specific performance criteria, such as for oil wiping.
A wiper made in accordance with the present invention includes a substrate layer that can adhere to the laminate layer, either through self-bonding or through the use of a separate adhesive bonding material. In particular, a substrate layer of the present invention is made from a fibrous material. In particular, a hydrophobic fibrous material can be used. Some examples of materials that are suitable for use in the substrate layer of the present invention are disclosed in U.S. Pat. No. 5,350,624 to Georger et al., which is incorporated in its entirety herein by reference thereto. Other examples of suitable substrate materials include, for example, meltblown polypropylene, spunbond polypropylene, HYDROKNIT(copyright) material, double recreped webs and tissue paper. In one particular embodiment of the present invention, the substrate layer comprises meltblown poly(ethylene vinyl acetate). One example of a commercially available form of poly(ethylene vinyl acetate) that is suitable for use in accordance with the present invention is EVA Grade LC 724.36, having a melt index of 135xc2x0 C., made by EXXON Chemicals.
The substrate layers employed in the present invention may exhibit various basis weights. In one particular embodiment, when laminate layers of approximately 49 gsm are employed, the total composite may have a basis weight of between about 125 gsm and 130 gsm, and more particularly about 130 gsm.
When adhered to the laminate layer according to the present invention, the substrate layer is believed to contain void spaces that can increase the ability of the wiper to hold moisture. Each time the wiper is subjected to a rinse cycle, the liquid within the wiper, including the liquid within the substrate layer, is totally or partially exchanged with liquid from an external source (e.g., a wash bucket). Liquid that enters the wiper generally has very little or no content of anti-microbial agent dissolved therein, and consequently is a poor anti-microbial solution. However, the liquid that is in contact with the subject substrate layerxe2x80x94and the anti-microbial agent in controlled release form that is adhered theretoxe2x80x94dissolves a portion of the anti-microbial agent and thereby forms an anti-microbial solution.
As used herein, the terms xe2x80x9canti-microbial solutionxe2x80x9d mean a liquid having in solution an amount of an anti-microbial agent that is sufficient to kill or reduce the growth rate of strains of common disease causing bacteria as compared with the same liquid without that amount of anti-microbial agent. In some of the embodiments of this invention, it is possible for the anti-microbial solution to act as a sanitizer solution or a disinfectant solution.
When the wiper is used to cleanse surfaces, some of the retained wiper liquid is forced out of the wiper and is left on the surface. Since this liquid is an anti-microbial solution, it is capable of acting as a biocide or biostat on the surface that has been wiped.
It is believed that because the substrate layer has a measurable and controllable void volume, the amount of liquid that is retained within the layer after a rinse can be determined and controlled. Accordingly, the anti-microbial agent that is adhered to the substrate layer must only provide enough anti-microbial agent to make this retained liquid an anti-microbial solution. Therefore, by controlling the amount and form of anti-microbial agent that is adhered to the substrate layer, and by providing the substrate layer as a fibrous mat having a measurable and controllable void volume, one is able to control the amount of anti-microbial agent that enters the retained liquid after each rinse cycle, and thereby to provide a wiper that is capable of replenishing the anti-microbial agent in the retained liquid after numerous rinse cycles.
It is believed that the use of a hydrophobic fibrous web as the substrate layer can also affect the fluid retention properties of that layer, and can thereby provide desirable control over the controlled-release characteristics of the wiper.
Furthermore, in one embodiment, the substrate layer is contained between two separate absorbent laminate layers, which allows the wiper to retain good wipe-dry properties, while also possessing the ability to hold moisture and prevent or reduce the loss of particles of a non-activated, highly concentrated, anti-microbial agent. An advantage of this structure is that it permits the isolation of anti-microbial agents from direct touch with any surface that the wiper contacts. This is an advantage when using anti-microbial agents that are irritating to the skin, because it prevents particles or concentrated sources of such agents from being left on surfaces which may come in contact with human skin (e.g., toilet seats). In addition, it is believed that such wipers tend to be less irritating to the hands of the user.
As stated above, a wiper of the present invention also includes an anti-microbial agent that can be controllably released. Generally, the anti-microbial agent is incorporated into the substrate layer of the subject wiper. In particular, the anti-microbial agent may be added to the substrate layer while the substrate layer remains in an unsolidified state. By being added at this stage, the anti-microbial agent can be highly dispersed and become part of the substrate layer""s fibrous web, thereby substantially prohibiting unwanted leakage of the agent. The cooling and solidification of the fibers into a structured web results in the adhesion of the particles to the substrate layer and substantially prevents them from being detached during repeating rinse cycles. The strength of adhesion of the particles to the substrate layer substantially prevents the migration of such particles from the substrate layer, and also reduces the loss of particles by abrasion.
In general, an anti-microbial agent of the present invention can comprise a number of different chemicals commonly used as disinfectants in the field. Useful anti-microbial agents include a chlorine dioxide-generating formulation containing chlorine dioxide, sodium chlorate surfactant, and an acid moiety as the anti-microbial agent. A commercially available example of such a controlled-release chlorine dioxide formulation is made by Bernard Technologies, Inc. and is sold under the name MICROSPHERE(copyright) 2500. This product may be described in U.S. Pat. Nos. 5,631,300; 5,639,295; 5,650,446; and 5,668,185.
In one embodiment of the present invention, the anti-microbial agent can include silver ions. In this embodiment, a silver-zeolite complex can be utilized to provide controlled release of the anti-microbial agent. One commercially available example of such a controlled-release anti-microbial agent has been available from AgION Technologies, LLC., under the name AgION(trademark) (which was previously available under the name HEALTH SHIELD(copyright) from K. B. Technologies, Inc.). This material has been incorporated into a fabric, which is available under the name GUARDTEX(copyright). This material is constructed from polyester and rayon and contains a silver-zeolite complex. Other suitable silver containing microbial agents are disclosed in Japanese Unexamined Patent No. JP 10/259325, which is incorporated herein by reference.
In addition to silver-zeolites, other metal-containing inorganic additives can also be used in the present invention. Examples of such additives include, but are not limited to, copper, zinc, mercury, antimony, lead, bismuth, cadmium, chromium, thallium, or other various additives, such as disclosed in Japanese Patent No. JP 1257124 A and U.S. Pat. No. 5,011,602 to Totani et al, which are incorporated herein by reference. In some embodiments, the activity of the additive can also be increased, such as described in U.S. Pat. No. 5,900,383 to Davis et al., which is also incorporated herein by reference.
In another embodiment of the present invention, the anti-microbial agent can be a material that is a source of free chlorine. Calcium hypochlorite or sodium hypochlorite can be used for this purpose, and calcium hypochlorite particles, in particular, can be useful. An example of a commercially available form of calcium hypochlorite particles suitable for use in the present invention is ALDRICH-brand #24-415-5 stabilized technical grade (ground and screened to approximately 150 micron particle size).
In addition to the above-mentioned embodiments, other anti-microbial agents can also be utilized in a wiper made in accordance with the present invention. Examples of such anti-microbial agents include, but are not limited to, quaternary amines, halogens, chlorine dioxide, oxidants, peroxides, such as sodium peroxide, other silver ions, such as Ag+, Ag++, and Ag+++ and silver complexes, or combinations thereof. Some examples of systems that can be used to generate chlorine dioxide, for instance, are disclosed in U.S. Pat. Nos. 5,126,070; 5,407,685; 5,227,168; 4,689,169; and 4,681,739, all of which are incorporated herein in their entireties by reference thereto. Another anti-microbial agent which could be employed is disclosed in U.S. Pat. No. 5,837,274 to Shick et al. which is incorporated herein in its entirety by reference thereto.
The anti-microbial agent of the present invention can be in a form that provides control of the rate of release of the agent from its source into the liquid that is in contact with the agent. A variety of mechanisms for adjusting solubility are known in the art and can be employed to control the release rate of the anti-microbial agent incorporated within a wiper made according to the present invention.
In some embodiments of the present invention, anti-microbial particles having varying sizes can be employed to control the release of the agents. For example, the release rate of calcium hypochlorite can be controlled by employing hypochlorite particles that have a certain size distribution. Because they provide higher surface area, smaller calcium hypochlorite particles have a faster dissolution rate into water than larger particles. Thus, in one embodiment of the present invention, the rate of calcium hypochlorite release by the wiper can be controlled by providing particles of different sizes. To reduce the overall release rate, larger particle sizes can simply be added as needed to the controlled-release composition prior to incorporation into the substrate layer.
An example of such an anti-microbial controlled-release agent is disclosed in PCT Application No. WO 98/53679, entitled xe2x80x9cSolid Disinfectant Material/Surfactant Compositionsxe2x80x9d and assigned to Olin Corporation. As described therein, disinfectant compositions are controllably released over time as anti-microbial agents.
In addition to varying particle size, other mechanisms for controlling release rate can be used to control the release of the anti-microbial agent present within a subject wiper. In particular, mechanisms for controlled release such as polymerization chemistries, encapsulation, porous absorbents, soluble binders, and other similar technologies can be employed to further enhance the ability to control the amount of anti-microbial agent released over a period of time.
For example, in one embodiment, calcium hypochlorite particles can be totally or partially encapsulated within a polymer coating to reduce the dissolution rate of the particles in water. By reducing the dissolution rate, the calcium hypochlorite is released in controlled amounts over a longer period of time, providing for the ability to withstand continued washing and rinsing, while still remaining effective as the anti-microbial agent of the wiper. When incorporating a coating with an anti-microbial agent of the present invention, any coating known in the art to reduce the release rate or dissolution rate of the agent can be used. For example, in one embodiment, an aqueous emulsion of an acrylic polymer is used to coat a calcium hypochlorite anti-microbial agent. In another embodiment, a microcrystalline wax coating can be used. In yet another embodiment, polyethylene can be used.
To sufficiently reduce the release rate of the anti-microbial agent in accordance with the present invention, it is not generally necessary to completely coat the particles. For instance, in one embodiment, a 20% acrylic polymer coating is used, while in another embodiment, a 33.5% acrylic polymer coating is used. In still another embodiment, a 60% microcrystalline wax coating is used.
According to the present invention, other chemicals can be incorporated into the subject wiper to enhance the performance of the wiper. For example, a wiper of the present invention can also contain surfactants, saponins, and other chemicals to control biofilm formation on the surface being cleaned. Furthermore, a wiper of the present invention can contain chemicals that act as visual sensors to detect the exhaustion of the anti-microbial agent. In particular, an indicator can be incorporated into a clear binder contained within the wiper to communicate an exhaustion of the anti-microbial agent by changing color. Several indicator methods are known in the art and may be utilized in the present invention. Examples include time indicators, chemical indicators, pH indicators, binder/dye indicators, and dye solubility indicators.
A method for producing an anti-microbial wiper of the present invention may be generally described as follows. It should be noted that the discussion below is intended only as a description sufficient to enable one skilled in the art to produce an embodiment of an anti-microbial wiper of the present invention. Other similar processes known in the art are also suitable for producing the anti-microbial wipers of the present invention.
To produce a wiper of the present invention, the anti-microbial agent is first generally entrapped within the substrate layer while the substrate layer remains in an unsolidified state. In particular, calcium hypochlorite particles, for example, may be entrapped within an unsolidified fibrous web of a poly(ethylene vinyl acetate) meltblown substrate layer. Other means could be employed, however, to attach the particles to the fibers. One example that could be utilized is disclosed in U.S. Pat. No. 5,736,473 to Cohen et al. which is incorporated herein in its entirety by reference thereto. Cohen et al. disclose a method of attaching a particulate material to individual surfaces of a fibrous material by employing an electrically charged matrix of fibrous material.
In one particular embodiment of the present invention, poly(ethylene vinyl acetate) (EXXON EVA Grade LC 724.36, melt index 135xc2x0 C.) is initially meltblown into a fibrous web. Processes and apparatuses employed for producing meltblown fibers and the resulting nonwoven webs are well known in the art. Meltblown fibers are fibers formed by extruding a molten polymeric material through a plurality of fine, usually circular, die capillaries as molten threads or filaments into converging, usually hot and high velocity, gas (e.g. air) streams to attenuate the filaments of molten material and form fibers. During the meltblowing process, the diameters of the molten filaments are generally reduced by the force exerted by the drawing air to a desired size. Thereafter, the meltblown fibers are carried by the high velocity gas stream and are deposited on a collecting surface to form a web of randomly disbursed meltblown fibers. Such a process is disclosed, for example, in U.S. Pat. No. 3,849,241 to Buntin et al, U.S. Pat. No. 4,526,733 to Lau, and U.S. Pat. No. 5,160,746 to Dodge, II et al., all of which are hereby incorporated herein in their entireties by reference thereto. Meltblown fibers may be continuous or discontinuous and are generally smaller than ten microns in average diameter. Various materials may be used to form the meltblown fibers such as polyethylene or polypropylene.
In one embodiment, poly(ethylene vinyl acetate) is extruded at a temperature such as 420xc2x0 F., at an extruder pressure of, for example, 135 psig, and at a primary attenuation air temperature of, for example, 435xc2x0 F. After extrusion, calcium hypochlorite particles (ALDRICH #24-415-5 stabilized granular technical grade) are then delivered to the meltblown poly(ethylene vinyl acetate) stream using a hopper apparatus having a regulated metering roll and are metered at 16.8 g/min (xcx9c12.4 g/m2) over a 7xe2x80x3 width of the meltblown ethyl vinyl acetate stream.
The discharge nozzle of the hopper apparatus is generally in close proximity to the hot exiting meltblown poly(ethylene vinyl acetate) fibers to facilitate adherence of the calcium hypochlorite particles to the molten fibers and to form the fibers into a consolidated web. The nozzle of the hopper apparatus may be spaced about 3 inches to about 4 inches, or less, away from the exiting fibers such that a consolidated web with a basis weight of approximately 24 grams per square meter can be formed.
After forming the poly(ethylene vinyl acetate)/calcium hypochlorite composite substrate layer, it is then necessary to bond the composite to one or more laminate layers for forming the subject hard surface wiper. A standard 49 gram per square meter HYDROKNIT(copyright) material may be employed as the absorbent laminate layer by being unwound upstream of the composite stream and positioned onto a foraminous forming wire operating at about 25 feet per minute. The tacky composite may then be formed directly onto the HYDROKNIT(copyright) material without adhering to the wire itself.
Thereafter, if desired, a second laminate layer may be adhered to the composite substrate layer. A second 49-gsm HYDROKNIT(copyright) material is likewise thermally bonded to the composite such that the substrate layer is positioned between the first and second laminate layers to act as an adhesive between the layers. In this regard, the spunbond sides of each layer of HYDROKNIT(copyright) material typically face the composite substrate layer.
After the three layers are appropriately positioned, a thermal bonder may be utilized to bond together the layers using a bond pattern (such as a xe2x80x9c714 bond patternxe2x80x9d as described in U.S. Pat. No. 5,389,202, which is incorporated herein in its entirety by reference thereto) roll positioned against a smooth steel roll. The roll parameters may be adjusted such that the roll temperature is, for example, about 214xc2x0 F., the bonding pressure is, for example, about 30 psig, and the line speed is, for example, about 10 feet per minute. As a result of the above described process, the anti-microbial agents (in one embodiment, calcium hypochlorite particles) are sufficiently positioned between the laminate layers within the substrate matrix such that only a negligible amount of particles are lost during mechanical working of the web when either dry or wet.